Solvent dyeing with aqueous perchloro-ethylene-hydrocarbon mixture and recovery of the solvents after dyeing

ABSTRACT

TEXTILE FIBERS ARE DYED IN A DYEBATH CONTAINING A MINOR PROPORTION OF WATER AND A MAJOR PROPORTION OF AT LEAST ONE INERT, WATER-IMMISCIBLE SOLVENT.

United. States Patent- I ssossls- I SOLVENT DYEING wi'rn AQUEOUS PERCHLORO- ETHYLENE HYDROCARBON MIXTURE AND RECOVERY on THE SOLVENTS AFTER DYEING Shlomo Rosenbaum, Berkeley, and Robert E. Foster,

Concord, ,Califl, assignors to .the United States of America as represented by the Secretary of Agriculture No Drawing. Filed Apr-10,1972, Ser. No. 246,025

Int. Cl. D061) 1/68 US. Cl. 8-94 a 1 Claim ABsTRAcron DISCLOSURE Textile fibers are dyed in a dyebath containing a minor proportion of .water and a ma or proportion of at least one inert, water-immiscible solvent.

A non-exclusive, irrevocable, royalty-free license in the invention herein;described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for suchpurposes, is hereby granted to the Government of the United States of America.

DESCRIPTION OF THE INVENTION The invention relates to and has'arnong its objects the ice Patented Apr. 23, 197.4

mits the use of water-soluble polar or ionic dyes, e.g.,

provision ofa novel method for dyeing fibers. Further objects of the invention will be evident from the following description wherein parts and percentages are by weight unless otherwise specified In the dyeing of textiles, water has been used as the medium from the very beginning of the art. Conventional dyeing operations require large quantities of water usually about 1050 times the weight of the fabric being treated. The disposal of the resulting spent liquors has created a major pollution problem. Adverse legislation and public opinion are forcing the industry to adequately treat spent dyeing liquors before they aredischarged into public waterways. Such activities, in turn, are leading to increased costs for the industry and, ultimately, for the consumer. I

Attemptshave been made at replacing water with an organic solvent whichcan berecovered easily by distillation, such as perchloroethylene. There are, however, several disadvantages. inherent in solvent dyeing. First of all, such solvents are not capable of dissolving polar or ionic dyes conventionally. used in aqueous systems and adapted for use with particular fibers. For example, acid dyes conconventional acid dyes adapted for dyeing of wool, direct dyes for cotton, etc.

The aqueous phase obtained in the solvent-recovery operation can be saved for future reuse in dyeing operations, or the water contained therein can be recovered by application of precipitation, ion-exchange, or other procedures well-known in the water treatment art. Because of the relatively small amounts of water involved, such recovery can be done easily and inexpensively.

DETAILED DESCRIPTION OF THE INVENTION In dyeing in accordance with the invention one pro ceeds as in conventional dyeing operations with the exception that the dye-bath employed is a 2-phase system.

One phase, that in minor proportion, is water containing dissolved therein a dye plus conventional adjuvants (e.g., sodium sulphate, sodium chloride, acid, etc.) as required by the dye and fibers in question. The other phase, that in major proportion, is a single inert, Organic, essentially water-immiscible solvent, or a mixture of two or more of such solvents.

Other factors in the dyeing operation are as in conventional dyeing. For example, wetting-out the fibers prior to dyeing, particular dye and adjuvants and the amounts thereof, temperature, and time of dyeing, etc. are selected in accordance with the usual principles of dyeing and thus may be varied over a wide range.

In a preferred embodiment of the invention the following steps are applied:

ventionally used in wool dyeing are not soluble in such organic solvents. Accordingly, the use of solvent dyeing systems will necessitate the development of appropriate solvent-soluble, non-polar dyes. Since dyes derive much of their afiinity forfibers from their polarity, the creation of suitable non-polar dyes becomes even more difiicult. Secondly, distillation procedures required for recovery of solvent from spent liquors are expensive and invariably involve a loss of material, usually to the atmosphere, thus causing an atmospheric pollution problem.

The invention described herein provides a means for obviating the problems outlined above. In accordance with the invention, fibers are dyed in a two-phase system in which the dye is dissolved in a minimum amount of Water, and which contains an inert water-immiscible solvent in an amount to make up the total volume of the dye-bath. At the completion of the dyeing operation the excess (unused) dye and dyeing adjuvants, being insoluble in the organic solvent, remain in the aqueous phase. The solvent can be readily recovered from the spent dye-bath by mechanical separation Without change of state, e.g., by decanting. Thus, the invention olfers an advantage over the use of an organic solvent in a one-phase system which requires a distillation step for recovery of solvent, and which distillation invariably results in loss of solvent; In the (I) The fibrous material to be dyed is entered into a suitable vessel which may take the form of a dye beck, packaging dyeing machine, or the like. The fibrous mate: rial is then wet-out with water, or more preferably with water containing a small percentage (for example, about 0.01 to 0.05%) of a conventional wetting agent. The amount of water required to wet-out the fibers will vary depending particularly on the nature of the fibers. Since it is a desideratum of the invention to use as little water as possible,a convenient plan to follow is to apply an excess of water preferably containing a wetting agent, allowing the fibers to soak thoroughly and then draining off that part of the water which has not been taken up by the fibrous material. Other expedients which may be employed to remove excess water include centrifuging and passing the fibrous material through squeeze rolls. Another expedientinvolves treating the fibrous material with the same organic solvent as employed in the dye-bath, in order to displace excess water. In any event, excellent results have been attained wherein the amount of water. retained in the fibrous material is about 0.6 to 1.5 parts of water per part of fibrous material. Usually it is preferred that no more than 1 part of water he retainedper part of fibrous material.

(II) -A Z-phase dye-bath is then prepared and entered into the vessel containing the wet-out fibers. Typically this dye-bath is prepared by compositing the organic solvent with an aqueous solution containing the dye. If any dyeing adjuvants such as sodium sulphate, sodium chloride, sulphuric acid, etc. are used, they are incorpo rated into the aqueous solution of the dye.

The total amount of the dye-bath will generally be about 10 to 50 parts thereof per part of fibrous material. The ratio of organic solvent to water is generally in the range of about 5 to 15 volumes of organic solvent per volume of water. The amount of dye dissolved in the water (the aqueous phase of the dye-bath) will vary with such factors as the nature of the dye, the fiber, and the level of dyeing desired. In many cases, one uses about 0.01% to 5% of active dye, based on the weight of the fibers. For example, for light dyeing about 0.01 to 0.5% is used; for medium dyeing, about 2%; for heavy dyeing, about 5%. The dye employed is obviously selected ac cording to color desired and ability to dye the fibers under treatment.

For use as the organic solvent in accordance with the invention, a wide choice of substances is available. One consideration is that the solvent should be essentially water-immiscible. Another item is that the solvent be inert, that is, unreactive with the fibers, water, the dye and other components of the dyebath. Also the solvent needs to be one in which the fibers, the dye, and the dyeing adjuvants are essentially insoluble. A further item is that the solvent be of low volatility; that, its boiling point should be at least 50 C., and preferably above 100 C. so it will not boil away at the elevated temperatures generally used in the dyeing operation, which are usually 50 to 100 C. Taking into account these considerations, there are many liquids which can be employed. Illustrative examples include perchloroethylene, trichloroethylene, ethylene dichloride, carbon tetrachloride, chloroform, benzene, toluene, xylenes, hexane, heptane, octane, mixtures of hydrocarbons including petroleum distillates such as naphthas, stoddard solvent, and the like, benzotrifluoride, 1,3-bis-(trifiuoromethyl) benzene, etc. For consideration of safety it is preferred to use a solvent which has a flash point above 100 C. It Will be understood that one may employ a single individual compound or mixtures of two or more compounds.

In a preferred embodiment one employs a solvent which has essentially the same density as the aqueous dye solution at the dyeing temperature, whereby to attain maximum dispersion of the aqueous dye solution in the organic solvent phase during the dyeing operation. This control of density can readily be achieved by combining two solvents in the pro-portions to produce the density desired. Typically, one may combine a chlorinated hydrocarbon (which has a density above 1) with a hydrocarbon such as a petroleum naphtha (which has a density below 1) to yield a composite solvent of the proper density.

(III) Having established the system of the fibers and the Z-phase dye-bath, the temperature thereof is raised to between 50 and 100 C. and maintained thereat during the dyeing cycle. As in conventional dyeing, it is necessary to maintain intimate contact and relative motion between the fibers and the dye-bath and this may be achieved by any suitable means such as stirring, rocking, tumbling, and the like, or by procedures that involve moving the fibrous material about in the bath, or by circulating the bath through the mass of fibrous material (as is the case with package dyeing machines). The contact of the fibrous material with the hot dye-bath is maintained for a period long enough to attain the desired level of coloration. In many cases this will be about from 1 to 6 hours.

(IV) After completion of the dyeing cycle, the dyebath is drained out of the dyeing vessel. The fibrous material is then rinsed with water or with the same organic solvent as used in the dyebath. In a preferred modification of the invention, the rinsing is carried out with a 2-phase rinse liquid containing water and any one or more of the organic solvents described herein in connection with the dyebath. Typically, this Z-phase rinse liquid will contain about 5 to 15 volumes of organic solvent per volume of water. After rinsing in any of the ways above described, the fibers are dried in conventional manner. To recover any organic solvent associated with the fibers, the vapors evolved during drying may be passed through recovery equipment to condense and collect the solvent.

(V) The effluent liquors such as the spent dyebath and rinse liquor are treated to recover the organic solvent therein. This can be done easily by allowing the liquor to stand to stratify the water and organic layers. If the liquor is hot, it may be allowed to stand until cooled sufficiently to stratify the Water and organic layers. Since the layers are stratified, mechanical separation as by decanting will serve to segregate the phases. The recovered organic solvent is saved for re-use in later dyeing and/ or rinsing operations. The separated aqueous phase can be reclaimed for future use by applying conventional purification procedures such as precipitation with alum, ion exchange, treatment with adsorbents such as clays or charcoal, etc.

Hereinabove it has been noted that dyeing in accordance with the invention is done with a dyebath containing two phases. The expression Z-phase dyebath used herein includes only those formulations which retain their character of containing two phases'even when subjected to vigorous agitation; it excludes formulations which yield emulsions or single-phase liquids upon agitation. The fact that our dyebath retains its 2-phase nature is advantageous in that at the end of the dyeing operation, the spent liquor can be readily separated into its components or organic solvent and Water containing residual dye. On the other hand with formulations that yield emulsions, the spent liquor cannot be mechanically separated into its components, and even separation by distillation is rendered diificult and inefficient.

In operating in accordance with the invention, we ensure the retention of the Z-phasecharacter of the dyebath by avoiding or at least limiting the addition of any emulsifying agents thereto. In the preliminarystep of wetting the fibrous material it is usually desirable to employ a wetting agent to promote penetration of water into the fibrous material. To prevent the wetting agent from causing emulsification during the dyeing operation, one may wash the fibrous material with plain water after it has been wet-out with water containing the wetting agent. Another plan is to use, in the wetting-out step, a surfactant which promotes wetting but which is not a good emulsifier. Among the agents which have such properties are sodium diisopropylnaphthalene sulphonate and sodium dibutylnaphthalene sulphonate. Other agents which have similar properties will be obvious to those skilled in the art.

The invention has wide versatility and can be applied for dyeing all kinds of fibers including natural fibers such as cotton, wool, silk, jute, linen, etc. and artificial fibers such as nylon, polyacrylonitrile and other acrylic fibers, viscose, etc. The fibers may be in any physical condition, e.g., bulk fibers, top, sliver, rovings, yarns, webbing, woven or knitted textiles, felts, garments and garment parts. The dye used in a practice of the invention may be any d'ye conventionally used in aqueous dyeing of textile fibers. Since it is desired that the dye remain in the aqueous phase, it is obvious that the dye selected be one which is soluble in water and essentially insoluble in organic solvents such as those used in application of the invention.

EXAMPLES The invention is further demonstrated by the following examples supplied by way of illustration and not limitat1on..

The proportion of various ingredients is expressed as the percentage based on the weight of fiber, this being abbreviated as percent o.w.f.

The expression PC solvent refers to a mixture of l volume of perchloroethylene and 2.1 volumes of Chevron Example 1.Acid dyeing The starting material was wool yarn which had been treated, in accordance with US. Pat. 3,391,986, by exposing it to a corona discharge zone into which is fed a mixture of air and chlorine gas.

The wool yarn (200 g.) was wound on a perforated spool which was placed in a laboratory-size package dyeing machine wherein the yarn was wet-out by first applying water containing 0.05% o.w.f. of wetting agent and then plain water. The amount of water retained by the yarn was about 200-250 g.

With the pump on, the following materials were added to the machine: 6.5 l. of PC solvent; 200 ml. of a aqueous solution of sodium sulphate (10% o.w.f.); and 40 ml. of 10% aqueous sulphuric acid (2% o.w.f.). Lastly, there was added 200 ml. of a 1% aqueous solution of Orange II (CII. acid orange 7).

The temperature of the system was raised to 88 C. and this temperature maintained for 75 minutes while continuing the pumping in the usual way to circulate the dyebath through the package of yarn.

The spent dyebath was drained out of the machine, allowed to stand, and the aqueous and organic solvent layers separated by decanting. The recovered solvent was clear and colorless.

The dyed wool yarn was then rinsed in the machine with the recovered organic solvent. The rinse liquor was drained out of the machine and the organic solvent separated from water by decanting, again yielding a clear and colorless solvent suitable for re-use.

The dyed yarn was dried in conventional manner and examined. It was found that the evenness of color was equivalent to that obtained by dyeing the same fiber in conventional manner. Moreover, the color of the product of the invention was slightly deeper than that of the conventionally dyed product.

An excellent dyeing was also obtained where the technique described above was applied to nylon-66.

Example 2.Direct dyeing A l-lb. package of cotton yarn was placed in a package dyeing machine wherein it was wet-out as described in Ex. 1. The amount of water retained in the yarn was about 1-1.5 lbs.

With the pump on, the following materials were added to the machine: 6.5 l. of PC solvent and, after raising the temperature to 77 C., 100 ml. of an aqueous solution of 5 g. of Calcod-ur Resin-Fast Blue 36 (C.I. direct blue 23-8). [in addition, g. of sodium chloride dissolved in 50 ml. of water was added in three portions over a minute period.

After continuing the dyeing at 77 C. for 70 minutes, the bath was drained out, allowed to stand, and the clear and colorless organic phase separated, and then used to rinse the dyed yarn.

The dyeing procedure as described above was repeated with cotton yarn and Superlitefast Yellow EPC {C.I. direct yellow 106).

In addition, viscose yarn was also dyed in the same manner, using the dyes noted above.

(In all four cases the color levels and evenness of dyeing were equivalent to those obtained by conventional dyeing procedures.

Example 3.--'Basic dyeing A ISO-gram package of Orlon acrylic yarn was placed in a package dyeing machine wherein it was wet-out as described in Ex. 1. The amount of water retained in the yarn was about 200 g.

With the pump operating, the following materials were added to the machine: 61. of PC solvent and, after raising the temperature to 45 C., 1.5 l. of water containing 0.75 g. of malachite green (C.I. basic green 4) and sufiicient acetic acid to provide a pH of 3.0. The dyeing was conducted at 8 8 C. for minutes.

The dyebath was dropped, the organic layer separated as described in Example 1, and the recovered organic solvent used to rinse the dyed yarn.

The color level and evenness of dyeing were again equal to that obtained by conventional dyeing.

Having thus described the invention, what is claimed is:

1. A process for dyeing textile fibers with minimum use of water, which comprises-- (A) contacting the fibers with a 2-phase dyebath, said dyebath containingone part by volume of water having dissolved therein a dye which is soluble in water but insolible in the organic solvent referred to below, an

about from 5 to 15 parts by volume of at least one inert organic solvent which is essentially waterimmiscible,

said dyebath being essentially free from any emulsifying agent so that it retains its 2-phase nature even when subjected to vigorous agitation,

(B) continuing said contact until a desired level of dyeing is attained,

(C) separating the dyed fibers from the deybath,

(D) allowing the dyebath to stratify to form an aque ous phase and an organic solvent phase, and then mechanically separating the aqueous phase from the organic solvent phase while retaining both of these phases in the liquid state, and

-(E) wherein said organic solvent is a mixture of- (i) 1 volume of perchloroethylene, and

(ii) 2.1 volumes of a mixture of mainly aliphatic hydrocarbons having the following properties: specific gravity 0.78, boiling range 31'1354 F., 50% over at 325 F.

References Cited UNITED STATES PATENTS 3,706,525 12/1972 Blackwell 8-93 2,274,751 3/194 2 Sowter 8-473 2,828,180 3/ 1958 Sertorio -8--62 3,523,749 8/ '1970 MacLeod et a1. 8-542 FOREIGN PATENTS 6710789 3/1968 Netherlands 8- 174 OTHER REFERENCES Peters et al.: J. Soc. Dyers & Col, March 1953 p. 183.

Translation of Henkel (Netherlands 6710789) above.

Miliceric: Solvent Dyeing: Theory & Practice, pp. 87- 93, J. Am. Assoc. of Tex Chem. & Colorist, vol. 2, No. 5, 1970.

DONALD LEVY, Primary Examiner US. Cl. XR. 

